Sewing up two meshes - unity3d

Question

Good afternoon! I'm trying to sew up two meshes. I do this as follows: first I convert the sprite into a mesh, then I duplicate the resulting mesh, shift it along the "z" axis, invert it, and then sew it up. But I faced such a problem: he sews rectangular meshes well, but in circular meshes there are some defects on the sides. So, how can you sew up these sides? (Materials and code)
public class ConvertSpriteInMesh : MonoBehaviour
{
public Sprite sprite;
private MeshDraft meshDraft = new MeshDraft();
private Mesh mesh;
void Start()
{
GetComponent<MeshFilter>().mesh = SpriteToMesh(sprite);
SewingUp();
}
/// <summary>
/// Sewing up nets
/// </summary>
private void SewingUp()
{
mesh = GetComponent<MeshFilter>().mesh;
meshDraft = new MeshDraft(mesh);
int leftVertical = mesh.vertices.Length / 2; // getting the beginning of the left vertical of the mesh
int index = mesh.vertices.Length;
for (int i = 0; i < leftVertical - 1; i++)
{
meshDraft.AddQuad(mesh.vertices[i], mesh.vertices[i+1], mesh.vertices[i + leftVertical + 1],mesh.vertices[i+leftVertical],
index);
index += 4;
}
GetComponent<MeshFilter>().mesh = meshDraft.ToMesh(); // assign the resulting mesh
}
/// <summary>
/// Convert Sprite to Mesh
/// </summary>
/// <param name="_sprite"></param>
/// <returns></returns>
private Mesh SpriteToMesh(Sprite _sprite)
{
// declaring variables
Mesh mesh = new Mesh();
Vector3[] _verticles;
int[] _triangle;
// assigning values
_verticles = Array.ConvertAll(_sprite.vertices, i => (Vector3)i);
_triangle = Array.ConvertAll(_sprite.triangles, i => (int)i);
// changing the size of the array
Array.Resize(ref _verticles, _verticles.Length * 2);
Array.Resize(ref _triangle, _triangle.Length * 2);
// adding another side
for (int i = 0; i < _verticles.Length / 2; i++)
{
_verticles[_verticles.Length / 2 + i] = new Vector3(_verticles[i].x, _verticles[i].y, 0.5f);
}
for (int i = 0; i < _triangle.Length / 2; i++)
{
_triangle[_triangle.Length / 2 + i] = _triangle[i] + (_verticles.Length / 2);
}
// invert the second side
for(int i = _triangle.Length / 2; i < _triangle.Length; i += 3) {
var temp = _triangle[i];
_triangle[i] = _triangle[i + 1];
_triangle[i + 1] = temp;
}
// assigning the mesh
mesh.vertices = _verticles;
mesh.triangles = _triangle;
mesh.RecalculateBounds();
mesh.RecalculateNormals();
return mesh;
}
}
public partial class MeshDraft {
public string name = "";
public List<Vector3> vertices = new List<Vector3>();
public List<int> triangles = new List<int>();
public List<Vector3> normals = new List<Vector3>();
public List<Vector4> tangents = new List<Vector4>();
public List<Vector2> uv = new List<Vector2>();
public List<Vector2> uv2 = new List<Vector2>();
public List<Vector2> uv3 = new List<Vector2>();
public List<Vector2> uv4 = new List<Vector2>();
public List<Color> colors = new List<Color>();
public MeshDraft(Mesh mesh) {
name = mesh.name;
vertices.AddRange(mesh.vertices);
triangles.AddRange(mesh.triangles);
normals.AddRange(mesh.normals);
tangents.AddRange(mesh.tangents);
uv.AddRange(mesh.uv);
uv2.AddRange(mesh.uv2);
uv3.AddRange(mesh.uv3);
uv4.AddRange(mesh.uv4);
colors.AddRange(mesh.colors);
}
public void AddQuad(Vector3 v0, Vector3 v1, Vector3 v2, Vector3 v3, int index, Color color = default(Color)) {
vertices.Add(v0);
vertices.Add(v1);
vertices.Add(v2);
vertices.Add(v3);
Vector3 normal0 = Vector3.Cross(v2 - v1, v3 - v1).normalized;
Vector3 normal1 = Vector3.Cross(v1 - v0, v2 - v0).normalized;
normals.Add(normal0);
normals.Add(normal0);
normals.Add(normal1);
normals.Add(normal1);
colors.Add(color);
colors.Add(color);
colors.Add(color);
colors.Add(color);
triangles.Add(index);
triangles.Add(index + 1);
triangles.Add(index + 2);
triangles.Add(index);
triangles.Add(index + 2);
triangles.Add(index + 3);
}
public Mesh ToMesh() {
var mesh = new Mesh { name = name };
mesh.SetVertices(vertices);
mesh.SetTriangles(triangles, 0);
mesh.SetNormals(normals);
mesh.SetTangents(tangents);
mesh.SetUVs(0, uv);
mesh.SetUVs(1, uv2);
mesh.SetUVs(2, uv3);
mesh.SetUVs(3, uv4);
mesh.SetColors(colors);
return mesh;
}
Successful stitching (screen)
Bad stitching (screen)

Answer 1

I was given an answer on another forum, who is interested, I will leave a link here - https://www.cyberforum.ru/unity/thread2823987.html